The invention relates to a switched capacitive voltage converter for converting an input voltage between an input terminal and reference terminal to an output voltage between an output terminal and the reference terminal.
Switched capacitive voltage converters of the type defined in the opening paragraph are known from the general state of the art. Switched capacitive voltage converters are used inter alia in battery-powered apparatuses, in which a high efficiency is important, because they make it possible to realize converters which have a high efficiency and which, in addition, generate low-level electromagnetic fields (also briefly referred to as EM fields), unlike converters which use a coil for the storage of energy.
For certain uses it is necessary to convert the input voltage to a higher output voltage. For these uses it is possible to employ, for example, switched capacitive voltage converters as described in European Patent Specification EP 0 461 717 A1. For other uses it is desirable to convert the input voltage to a lower output voltage. For the last-mentioned uses it is possible to employ, for example, switched capacitive voltage converters as described in U.S. Pat. No. 4,389,704.
There are also uses, such as for example the so-called class G audio amplifiers, where it is desirable for reasons of efficiency that at a given instant the input voltage is converted to a higher output voltage and at another instant the input voltage is converted to a lower output voltage.
A drawback of the switched capacitive voltage converters as described in said European Patent Specifications is that they can operate solely as an up converter and a down converter, respectively, but not as a combined up/down converter.
Switched capacitive up/down converters are known from the general state of the art but these are made up of a separate opening converter and a separate down converter. A drawback is that they require a comparatively large number of components. Particularly in the case of use in an integrated circuit (IC) it is important to minimize the number of capacitive elements because these elements occupy a comparatively large portion of the required chip area.
Another drawback of the afore-mentioned capacitive up/down converters in accordance with the generate state of the art is that they require a comparatively large number of IC pins for the connection of external components.
A further drawback of the afore-mentioned capacitive up/down converters in accordance with the general state of the art is that they dissipate comparatively much power.